Week Two Day One

Josie, Greytown

The green lake landslide
New Zealand’s largest recorded landslide occurred about 13,000 years ago in Fiordland. About 27 cubic kilometres of material collapsed in a deadly landslide that covered an area of over 45 square kilometres. Because of it, a huge chunk of a mountain range collapsed into the valley below. Some dents in the surface filled with water, forming sizable holes such as Green Lake, rather than the usual ponds.

Emma, Greytown

A notable New Zealand landslide - The Abbostford landslide...On August 8th of 1979 lots of the Dunedin suburb slid down Abbotsford. No-one was hurt but seventeen people and many houses were taken with it. Sixty nine of these house were ruined and no longer able to be lived in. More then ten years earlier they had started to notice problems, but it moved very slowly and had not been a problem until that day in 1979. The slide moved about three metres per minute. Here is some information I found on the internet put into easier to understand words...
The Abbotsford landslide was a layered rock landslide – a layered landlside is when the hill slides on a lubricated (which means slippery or wet) layer of clay. The same rock formations which are often known as mudstone, sometimes cause unpredictable slopes in a place just north of Dunedin, on the Kilmog Hill. Signs of slope movement is able to be seen in the smooth, slippery surface of State Highway 1 in this area.

Madison,Greytown

The young river landslide in Mt Aspiring national park is the biggest landslide in New Zealand since the top of Mt Cook fell off.
Geologists found out using a tripod-laser scanner that the landslide was 13 million cubic metres.
The Mt Cook landslide in 1991 was 16 million cubic metres.

Kaden, Greytown

Waihī Landslide

New Zealand’s highest death toll from a landslide was in the 1846 Waihī disaster, it claimed 60 lives on the shores of Lake Taupō. After heavy rains a landslide blocked a stream, creating a dam behind it. Three days later the dam collapsed sending a mudflow down the river overflowing it and killing many Maori people.

Tig (Greytown)

The Mount aspiring landslide buried an alpine lake nearby. THAT must've been HUGE!!

Sophie, Greytown

Abbortsford Landslide

On the night of August 8th (My birthday) 1979 a huge landslide occurred in Abbortsford, causing the destruction or relocation of 70 houses, and over 600 people were asked t leave their home. Luckily no one was killed. This remains the biggest landslide in an urban area in New Zealand.
18 years before this happened a report from Otago University stated that the soil in Abbortsford was unsuitable for building houses on, due to it be unstable. The report must of been lost or ignored because in the 1960’s the first housing was built.
In 1979 the ground began to give way, and by the 5th of August 17 houses were evacuated. A gap in the road became a huge chasm as the landslide happened, and hundreds were left homeless.

jelmer,Greytown

Abbotsford

On 8 August 1979 a huge area of the Dunedin suburb of Abbotsford slid downhill, taking 17 people and many houses with it. Luckily no one was hurt – but 69 houses were left uninhabitable. The trouble had started more than a decade earlier when residents noticed hairline cracks in concrete paths. The slip moved very slowly until the sudden slide in 1979, which moved at around 3 metres per minute.

Water Under the Bridge.

This is an extra!
If you found the work on using cubic metres to measure volume interesting you might try this.
The flow of rivers and streams is measured in cumecs, that is, cubic metres per second. Imagine your local stream/river pouring into the cubic metre you made earlier to measure the Mt Cook rock fall. How many times do you think it would be filled in one second?
Ask your teacher or Mum and Dad if you can explore the flow of a local stream / river. It must be small enough for you to wade across. You must make sure it is a safe thing to do and it would be good to do with an adult and other children.
You will need a metre rule, a measuring tape, a stop watch and of course pencil and graph paper and something like a table tennis ball (or a little plastic duck or even a Pooh Stick as long as it floats).
Find an open piece of the stream (the flatter the bottom the better) and measure the distance from side to side on the surface. Note this down and draw it to scale on a graph paper. Make one square equal to a known measurement. E.g. One square equals 25 centimetres. Now, using the metre ruler take a depth reading every ten, twenty five of even fifty centimetres (depending on the width of the steam. Transfer these measurements to the surface drawing using the same scale you used for the width. Now you will need to do a bit of tricky maths to try and find the area of the profile - you can use the squares on the graph paper to help. Sometimes you can take the sloping bit off one side and add it to the other to get a bit of a rectangle. You should end up with a an area in square centimetres or metres. Now to turn this into volume.
Find a place where the flow is as direct as possible, in other words something will float in a straight line. Mark a point on the bank and drop the table tennis ball into the current opposite it. As you do this start the stop watch - call out the seconds (probably 5, but it will depend on the speed of the stream). On 5 get a partner to mark where the ball has got to. Measure and write down the distance. Do this 5 times to get an average flow. Add up the 5 totals and divide by 5, this gives you the average. Now divide this by 5 to find out how far the ball traveled in 1 second. Multiply this by the area of your profile and you have your cumecs.
You can now work out how much water flows under the bridge in a minute? In an hour? In a day? In a year? Remember this is normal flow - it will change.
Now go and do some research on bigger rivers - the Waikato, the Clutha and the biggest of them all the Amazon.If you have anything you would like to share put it here.
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A Swimming Pool Fell On My Head!

This is an extra!
Farmers, gardeners and schools kids take great interest in the weather, especially the wet parts of the weather. In all parts of the country the rainfall is measured and these figures are used to decide on crop planting, harvesting, power generation, or whether you take a rain coat etc.
But did you ever stop and think about how much rain falls on you? No! Well now is your chance.
Go to http://www.niwa.cri.nz/edu/resources/climate/meanrain and download the spreadsheet that gives mean rainfall totals for many places around NZ. Pick one close to you or use records that are kept locally. Now mark out an area 10 metres square on the court and, using the spreadsheet and water volume and weight things you have already worked out in earlier challenges find out the total weight of the rainfall on that patch of court in a year. The Wairarapa Valley (Masterton's rainfall) is about 100 km long and 10 km wide. I wonder what the water that fell on the whole valley weighed?
Have a look at http://www.emigratenz.org/ReallyAndTruly.htmland think about the impact of that wee shower.
Next time it rains have a think about how heavy clouds are!Heavy air? A bit more on why clouds float.If you have anything you would like to share put it here.
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